Not sure if you are asking, if there is a way change the monitor window it is recording or if you can recover the video for the post you tried to record? If it is the second option then there is nothing that can be done to recover the video because it was just not recorded at least not the part you needed.
If it is the first option then locate the SELECT RECORDING WINDOW section on the lower left of the Debut main window and select the icon that shows a small monitor with 4 arrows on each corner of the screen, then select either the primary or secondary monitors.